Mysterious blasts of energy producing more explosive power than anything else in the universe date back almost to the dawn of time, according to new research by astronomers.

Gamma-ray bursts, first spotted in the 1960s, create more energy in just 10 seconds than the sun will produce in the whole of its 10 billion year life.

Astronomers from the University of Cambridge have calculated that the dimmest bursts detected are so far away, their light has taken nearly the whole of the time the universe has existed, to reach us.

They would have occurred at the time the first stars and galaxies were being formed shortly after the Big Bang, which created all the matter in the universe about 15 billion years ago.

Cause still unknown

The discovery also means gamma-ray bursts are about 20 times more powerful than had previously been estimated and appear to dwarf supernovas (exploding dying stars).

Thousand of gamma-ray bursts have been observed by Nasa's Compton Gamma Ray Observatory satellite but scientists still do not fully understand what causes them.

There were even suggestions that they might be the exhaust trails of alien spaceships but the general agreement now is that the radiation flashes are somehow linked to the death of massive, short lived stars.

Explosions theory

The Cambridge astronomers reached their latest conclusions by comparing the strengths of large numbers of gamma-ray bursts with predictions based on the theory the explosions are linked to the death of stars.

Using this information they were able to calculate how many bursts it should be possible to see from different eras in the universe's history.

They found their answers tallied with actual observations.

Dr Ralph Wijers, leading the team at Cambridge University's Institute of Astronomy, said: "These events come from a time in the evolution of the universe from which up to now we have had little or no information.

"Gamma-ray bursts may be a small corner of astrophysics, but there are important implications for discovering what the early universe was like."

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